(This video requires some knowledge of object relations theories) Intuitively, a connection between SPD and the Narcissistic Personality Disorder (NPD) seems plausible. After all, narcissists are people who self-sufficiently withdraw from others. They love themselves in lieu of loving others. Lacking empathy, they regard others as mere instruments, objectified "Sources" of Narcissistic Supply.
Schizoids are often described, even by their nearest and dearest, in terms of automata ("robots"). They are uninterested in social relationships or interactions and have a very limited emotional repertoire. It is not that they do not have emotions, but they express them poorly and intermittently. They appear cold and stunted, flat, and "zombie"-like.
Consequently, these people are loners. They confide only in first-degree relatives, but maintain no close bonds or associations, not even with their immediate family. Naturally, they gravitate into solitary activities and find solace and safety in being constantly alone. Their sexual experiences are sporadic and limited and, finally, they cease altogether.
Schizoids are anhedonic - find nothing pleasurable and attractive - but not necessarily dysphoric (sad or depressed). Some schizoid are asexual and resemble the cerebral narcissist. They pretend to be indifferent to praise, criticism, disagreement, and corrective advice (though, deep inside, they are not). They are creatures of habit, frequently succumbing to rigid, predictable, and narrowly restricted routines.
(From the book "Malignant Self-love: Narcissism Revisited" by Sam Vaknin - Click on this link to purchase: http://www.narcissistic-abuse.com/thebook.html)